Kerry expressed disappointment that the legislation, introduced in 2009, has been enacted.
"For the four years since the bill was introduced, we have been crystal clear that it blatantly violates human rights obligations that Uganda’s Human Rights Commission itself has recognized are enshrined in Uganda’s Constitution."
The enactment of the Anti-Homosexuality Bill, Kerry said, "threatens a dangerous slide backward in Uganda’s commitment to protecting the human rights of its people and a serious threat to the LGBT community in Uganda," as well as potentially threatening public health efforts to address HIV/AIDS.
"This is a tragic day for Uganda and for all who care about the cause of human rights. Ultimately, the only answer is repeal of this law."
Under the new law, those found guilty of "aggravated homosexuality" may face life in prison. Outreach to gays and lesbians may also result in prison time, a provision that could impact rights groups and LGBT support and service providers.
Ugandan President Yoweri Museveni, speaking to CNN, said, "We have been disappointed for a long time by the conduct of the West, the way you conduct yourselves there. ... Our disappointment is now exacerbated because we are sorry to see that you live the way you live, but we keep quiet about it. Now you say 'you must also live like us' -- that's where we say no."